|Publication number||US7011420 B2|
|Application number||US 10/234,553|
|Publication date||Mar 14, 2006|
|Filing date||Sep 4, 2002|
|Priority date||Sep 4, 2002|
|Also published as||US20040042198|
|Publication number||10234553, 234553, US 7011420 B2, US 7011420B2, US-B2-7011420, US7011420 B2, US7011420B2|
|Inventors||Ronald S. Cok|
|Original Assignee||Eastman Kodak Company|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (10), Referenced by (11), Classifications (11), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates to the use of organic light emitting diodes for area illumination, and more particularly to directed area illumination such as is provided by a spotlight.
The light emitting elements in conventional bulbs (the filament of an incandescent bulb or the fluorescent material in a fluorescent bulb) are extremely bright and emit light in every direction. In many applications, directed lighting is preferred, for example with spotlights, floodlights, or track lighting. For these applications, traditional lighting devices such as incandescent or fluorescent light bulbs typically require reflectors or lenses to direct the light output. For example, desk, table, floor and ceiling lamps conventionally use shades to reflect light to the ceiling or floor to provide indirect lighting suitable for use in a home or office environment. Spotlights or floodlights place the lighting element within a curved reflector to direct the light. Thick glass conventional lenses and fresnel lenses are often employed to both refractively direct the light emitted and to seal the lighting elements. These reflectors and lenses are expensive, may be heavy, and take considerable space.
Solid-state lighting devices made of light emitting diodes are increasingly useful for applications requiring robustness and long-life. For example, solid-state LEDs are found today in automotive applications. These devices are typically formed by combining multiple, small LED devices providing a point light source into a single module together with glass lenses or reflectors suitably designed to direct the light as is desired for a particular application; see for example, WO99/57945, published Nov. 11, 1999. These multiple devices are expensive and complex to manufacture and integrate into single illumination devices.
Organic light emitting diodes (OLEDs) are manufactured by depositing organic semiconductor materials between electrodes on a substrate. This process enables the creation of light sources having an extended light emitting surface area on a single substrate. The prior art describes the use of electro-luminescent materials as adjuncts to conventional lighting; see for example U.S. Pat. No. 6,168,282, issued Jan. 2, 2001 to Chien. In this case, because of the limited light output from the electro-luminescent material, it is not useful for primary lighting.
EP1120838A2, published Aug. 1, 2001 describes a method for mounting multiple organic light emitting devices on a mounting substrate to create a light source. However, the light source is not directed.
There is a need therefore for an improved OLED lighting apparatus for directed illumination having a simple construction that provides a highly integrated and robust light.
The need is met by providing a solid-state area illumination light source that includes a planar substrate, a non-pixellated organic light emitting diode (OLED) layer deposited on the planar substrate, the organic light emitting diode layer including first and second electrodes for providing electrical power to the OLED layer, an encapsulating cover covering the OLED layer; first and second conductors electrically connected to the first and second electrodes, and extending beyond the encapsulating cover for making electrical contact to the first and second electrodes by an external power source; and a lenslet array located on the substrate and/or encapsulating cover and coextensive with the OLED layer for directing the light emitted by the OLED layer.
The present invention has the advantage of providing an inexpensive, long lived, highly efficient, lightweight, low volume directed light source that provides directed illumination in a small package.
It will be understood that the figures are not to scale since the individual layers are too thin and the thickness differences of various layers too great to permit depiction to scale.
The cover 22 may be a separate element such as a hermetically sealed cover plate affixed over the layers 12, 14, and 16 or the cover may be coated over the layers 12, 14, and 16 as an additional layer. The OLED light emitting layer 12 is continuous over the substrate to provide a continuous light emitting area. First and second conductors 24 and 26 located on the substrate 20 are electrically connected to the first and second electrodes 14 and 16, and extend beyond the encapsulating cover 22 on extension 20″ for making electrical contact to the first and second electrodes by an external power source (not shown). This power source may be mounted in a portable apparatus that includes the light source 10 (as in a flashlight) or separately connected through a socket 34 to a power cable 46. The cable may be detachable from the light source or permanently affixed.
To allow light to be emitted from the OLED light source 10, the substrate 20, the electrodes 14 and 16, and the cover 22 are transparent. In applications where it is not required to emit light from both sides of the substrate, one or more of the substrate, cover, anode, or cathode may be opaque or reflective. The substrate 20 and/or cover 22 may be suitably treated to provide directional lighting in one direction only. For example, the cover, substrate, or one of the electrodes may be provided with a reflective surface so that light emitted by the OLED layer will travel through the other surface and the device will emit light from only one side.
The lenslet array 11 may take a variety of forms depending on the application desired. In a preferred embodiment, the lenslet array is a flat layer embossed or molded on either or both the substrate 20 and/or the encapsulating cover 22. In one embodiment, the lenslet array is coextensive with the light emitting layer 12 of the device. For example, a multiplicity of separate lenses may be embossed or molded into the cover and/or the substrate. In an alternative embodiment, the lenslets are embossed into a separate layer, for example a plastic sheet, which is applied to the substrate and/or encapsulating cover over the light emitting area. The lenslets may be identical across the array or elements at the edge may differ from those in the center to further direct the light in a preferred way.
As a general rule, the focal length of a short focal length lens is on the order of its diameter. In the present invention, the lenslet array(s) is applied directly to the substrate and/or cover of the light emitters. In an OLED lamp, this distance can be as small as a millimeter. The lenslet arrays should have a similar focal length and be as small as possible, a millimeter or less. The shape of the lenslet arrays can vary depending on the desired application, for example conventional convex lenses, pyramids 36 (as shown in
Because both the lenslet arrays 11 and the OLED light source 10 are flat, the present invention enables a very flat area illumination light source that directs light in a preferred way.
The substrate 20 can be either rigid or flexible. Rigid substrates, such as glass, provide more structural strength and are generally planar and may have a variety of shapes other than rectangular. The present invention may also be used with a flexible substrate, such as plastic. If a flexible substrate is used, the flexible transparent substrate may be attached to a rigid support or held within a frame. The frame may be opaque or transparent depending on the lighting and decorating needs of the application.
The present invention may be powered by a variety of sources, for example from standard AC power (such as 110 volts AC or 220 volts AC) available in households or offices. If necessary, conventional power conversion devices may be employed to provide power suitable for used by the light emitting layer 12. Alternatively, DC sources found in vehicles or through batteries may be used, for example 24, 12, or 6 volt DC sources with appropriate converters to obtain a desired operating voltage and waveform.
The present invention has the added advantage that the directed light source has a compact planar configuration enabling efficient storage, packing, and shipping.
In a preferred embodiment, the invention is employed in an area illumination device that includes an Organic Light Emitting Diode (OLED) which is composed of small molecule or polymeric OLED materials as disclosed in but not limited to U.S. Pat. No. 4,769,292, issued Sep. 6, 1988 to Tang et al., and U.S. Pat. No. 5,061,569, issued Oct. 29, 1991 to VanSlyke et al. The light source may also include multiple light emitting layers as described in commonly assigned U.S. patent application Ser. No. 10/231,853 filed Aug. 7, 2002 by Tyan now U.S. Pat. No. 6,693.296), and U.S. Ser. No. 10/077,270 filed Feb. 15, 2002 by Liao et al., the disclosures of which are incorporated herein by reference.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
OLED light source
organic light emitting layer
light emissive portion of substrate
extension of substrate
sheet having lenslet array
|Cited Patent||Filing date||Publication date||Applicant||Title|
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|Citing Patent||Filing date||Publication date||Applicant||Title|
|US7535171||Jun 21, 2007||May 19, 2009||Advantech Global, Ltd.||System and method for total light extraction from flat-panel light-emitting devices|
|US7710031 *||Aug 12, 2003||May 4, 2010||Zeon Corporation||Lens array sheet|
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|US7999485||Dec 1, 2008||Aug 16, 2011||Pass & Seymour, Inc.||Electrical device|
|US8083390||Oct 12, 2007||Dec 27, 2011||Koninklijke Philips Electronics N.V.||Lighting device employing a light guide plate and a plurality of light emitting diodes|
|US8605338||Jun 14, 2011||Dec 10, 2013||Xerox Corporation||User feedback via see through platen overlay|
|US9291337||Nov 17, 2014||Mar 22, 2016||William L. Hulett||LED dent repair and detail light|
|US20050212989 *||Aug 12, 2003||Sep 29, 2005||Motofumi Kashiwagi||Lens array sheet|
|US20080043475 *||Jun 21, 2007||Feb 21, 2008||Advantech Global, Ltd.||System and method for total light extraction from flat-panel light-emitting devices|
|US20110051456 *||Oct 12, 2007||Mar 3, 2011||Koninklijke Philips Electronics N.V.||Lighting device employing a light guide plate and a plurality oflight emitting diodes|
|US20110310625 *||Dec 22, 2011||Abl Ip Holding Llc||Light Fixtures Comprising Organic Light Emitting Diodes|
|U.S. Classification||362/84, 362/800, 362/244, 362/333|
|Cooperative Classification||Y10S362/80, H01L51/5275, H01L2251/5361, H01L2251/5323, F21Y2105/008|
|Sep 4, 2002||AS||Assignment|
Owner name: EASTMAN KODAK COMPANY, NEW YORK
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:COK, RONALD S.;REEL/FRAME:013274/0547
Effective date: 20020903
|Aug 21, 2009||FPAY||Fee payment|
Year of fee payment: 4
|Feb 26, 2010||AS||Assignment|
Owner name: GLOBAL OLED TECHNOLOGY LLC,DELAWARE
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:EASTMAN KODAK COMPANY;REEL/FRAME:023998/0368
Effective date: 20100122
Owner name: GLOBAL OLED TECHNOLOGY LLC, DELAWARE
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:EASTMAN KODAK COMPANY;REEL/FRAME:023998/0368
Effective date: 20100122
|Mar 14, 2013||FPAY||Fee payment|
Year of fee payment: 8